Asphalt composition

ABSTRACT

An asphalt composition comprising 0.5 to 50 parts by weight of a block copolymer component (I), 100 parts by weight of an asphalt (II) and 0.01 to 10 parts by weight of at least one vulcanizing agent (III) selected from the group consisting of sulfur and a sulfur-containing compound, wherein the block copolymer component (I) comprises at least one modified block copolymer comprising an unhydrogenated or hydrogenated base block copolymer comprising at least one vinyl aromatic polymer block (A) and at least one conjugated diene polymer block (B), and a functional group-containing modifier group bonded to the base block copolymer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an asphalt composition. Moreparticularly, the present invention is concerned with an asphaltcomposition comprising a block copolymer component (I), an asphalt (II)and at least one vulcanizing agent (III) selected from the groupconsisting of sulfur and a sulfur-containing compound, wherein the blockcopolymer component (I) comprises at least one modified block copolymercomprising a base block copolymer comprising at least one vinyl aromaticpolymer block (A) and at least one conjugated diene polymer block (B),and a functional group-containing modifier group bonded to the baseblock copolymer. The asphalt composition of the present invention isadvantageous not only in that it has a high softening point andexcellent properties with respect to ductility, storage stability athigh temperatures and flexural properties at low temperatures, but alsoin that, when the asphalt composition is used in road paving, there canbe formed a pavement layer having excellent dynamic stability andexcellent aggregate-gripping properties. Therefore, the asphaltcomposition of the present invention is very suitable for use in roadpaving. Thus, the asphalt composition of the present invention can beadvantageously used as a binder for road paving, especially as a binderfor forming a drainage pavement.

2. Prior Art

Conventionally, an asphalt composition has been used in a wide varietyof fields, such as the fields of a material for use in road paving, amaterial for a waterproof sheet, a material for a sound insulating sheetand a roofing material. In these fields, a number of attempts have beenmade to improve the properties of the asphalt composition by addingvarious polymers to the asphalt composition. As examples of suchpolymers, there can be mentioned an ethylene/vinyl acetate copolymer, anethylene/ethyl acrylate copolymer, a rubber latex, and a block copolymercomprising conjugated diene monomer units and vinyl aromatic hydrocarbonmonomer units.

However, in recent years, due to the expansion of traffic and theincrease in the number of expressways, there is a growing demand for anasphalt mixture (which is comprised of a plurality of aggregates and anasphalt composition as a binder) having excellent strength and excellentabrasion resistance. Further, there is a growing demand for an asphaltmixture which not only has excellent strength and excellent abrasionresistance, but also can be used to form a highly open graded pavementlayer which can improve the drainage properties and noise reductionproperties of expressways. For achieving the above-mentioned excellentproperties, the asphalt composition is required to have a high softeningpoint and high mechanical strengths (such as high flexural stress andexcellent aggregate-gripping properties). For meeting this requirement,it has been attempted, for example, to employ a method in which a blockcopolymer having a high molecular weight is incorporated into theasphalt composition. However, such method is disadvantageous in that theresultant asphalt composition containing a high molecular weight blockcopolymer incorporated therein has unsatisfactory storage stability athigh temperatures and, hence, its melt viscosity becomes increased underhigh temperature conditions, thus rendering poor the workability of theasphalt composition during the road paving.

For improving the storage stability of an asphalt composition at hightemperatures, it has generally been attempted to add an aromatic processoil to the asphalt composition, or effect a crosslinking of the asphaltcomposition by the use of sulfur or a peroxide. For example, ExaminedJapanese Patent Application Publication No. Sho 57-24385 (correspondingto U.S. Pat. No. 4,145,322) discloses a crosslinking using sulfur. Onthe other hand, Examined Japanese Patent Application Publication No. Hei1-13743 (corresponding to U.S. Pat. Nos. 4,554,313 and 4,567,222)discloses a crosslinking using a polysulfide having a specificstructure. Further, Unexamined Japanese Patent Application Laid-OpenSpecification No. Hei 3-501035 (corresponding to U.S. Pat. No.5,508,112) discloses a crosslinking using a combination of sulfur as avulcanizing agent and a sulfur-containing compound as a vulcanizationaccelerator. However, any of the above-mentioned techniques is stillunsatisfactory in improving the storage stability of an asphaltcomposition at high temperatures. Also, it has been desired to developan asphalt composition which not only has excellent storage stability athigh temperatures, but also can be used for forming a pavement layerhaving excellent dynamic stability and excellent aggregate-grippingproperties.

SUMMARY OF THE INVENTION

In this situation, the present inventors have made extensive andintensive studies with a view toward solving the above-mentionedproblems accompanying the prior art. In their studies, the presentinventors have focused on improvement of the properties of an asphaltcomposition containing an unhydrogenated or hydrogenated block copolymercomprising vinyl aromatic hydrocarbon monomer units and conjugated dienemonomer units, and an asphalt. As a result, it has unexpectedly beenfound that the above objective can be attained by an asphalt compositioncomprising a block copolymer component (I), an asphalt (II) and at leastone vulcanizing agent (III) selected from the group consisting of sulfurand a sulfur-containing compound, wherein the block copolymer component(I) comprises at least one modified block copolymer comprising a baseblock copolymer comprising at least one vinyl aromatic polymer block (A)and at least one conjugated diene polymer block (B), and a functionalgroup-containing modifier group bonded to the base block copolymer. Thatis, such asphalt composition has been found to be advantageous not onlyin that it has a high softening point and excellent properties withrespect to ductility, storage stability at high temperatures andflexural properties at low temperatures, but also in that, when theasphalt composition is used in road paving, there can be formed apavement layer having excellent dynamic stability and excellentaggregate-gripping properties. It has also been found that, when amixture of specific different block copolymers is used as the blockcopolymer component (I), the asphalt composition has a good balance ofthe softening point and the melt viscosity. Based on these novelfindings, the present invention has been completed.

Accordingly, it is an object of the present invention to provide anasphalt composition which is advantageous not only in that it has a highsoftening point and excellent properties with respect to ductility,storage stability at high temperatures and flexural properties at lowtemperatures, but also in that, when the asphalt composition is used inroad paving, there can be formed a pavement layer having excellentdynamic stability and excellent aggregate-gripping properties.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following detailed description andappended claims.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, there is provided an asphaltcomposition comprising:

0.5 to 50 parts by weight of a block copolymer component (I) comprisingat least one modified block copolymer comprising:

a base block copolymer comprising at least one vinyl aromatic polymerblock (A) composed mainly of vinyl aromatic hydrocarbon monomer unitsand at least one conjugated diene polymer block (B) composed mainly ofconjugated diene monomer units, and

a modifier group bonded to the base block copolymer, the modifier grouphaving at least one functional group,

the base block copolymer being unhydrogenated or hydrogenated,

100 parts by weight of an asphalt (II), and

0.01 to 10 parts by weight of at least one vulcanizing agent (III)selected from the group consisting of sulfur and a sulfur-containingcompound.

For easy understanding of the present invention, the essential featuresand various preferred embodiments of the present invention areenumerated below.

-   1. An asphalt composition comprising:

0.5 to 50 parts by weight of a block copolymer component (I) comprisingat least one modified block copolymer comprising:

a base block copolymer comprising at least one vinyl aromatic polymerblock (A) composed mainly of vinyl aromatic hydrocarbon monomer unitsand at least one conjugated diene polymer block (I) composed mainly ofconjugated diene monomer units, and

a modifier group bonded to the base block copolymer, the modifier grouphaving at least one functional group,

the base block copolymer being unhydrogenated or hydrogenated,

100 parts by weight of an asphalt (II), and

0.01 to 10 parts by weight of at least one vulcanizing agent (III)selected from the group consisting of sulfur and a sulfur-containingcompound.

-   2. The asphalt composition according to item 1 above, wherein the    block copolymer component (I) is a mixture of:

10 to 90% by weight of a modified block copolymer (I-A) comprising:

a base block copolymer comprising at least two vinyl aromatic polymerblocks (A) and at least one conjugated diene polymer block (B), and

the modifier group bonded to the base block copolymer,

the base block copolymer being unhydrogenated or hydrogenated; and

90 to 10% by weight of at least one block copolymer selected from thegroup consisting of:

a modified block copolymer (I-B) other than the modified block copolymer(I-A), which comprises:

a base block copolymer comprising at least one vinyl aromatic polymerblock (A) and at least one conjugated diene polymer block (B), and

the modifier group bonded to the base block copolymer,

the base block copolymer being unhydrogenated or hydrogenated, and

an unmodified block copolymer (I-C) comprising at least one vinylaromatic polymer block (A) and at least one conjugated diene polymerblock (B), the unmodified block copolymer (I-C) being unhydrogenated orhydrogenated,

wherein each % by weight is based on the weight of the mixture.

-   3. The asphalt composition according to item 1 or 2 above, wherein    the modifier group has at least one functional group selected from    the group consisting of the functional groups represented by the    following formulae (1) to (14):

-   -   wherein, in formulae (1) to (14):        -   N represents a nitrogen atom, Si represents a silicon atom,            O represents an oxygen atom, C represents a carbon atom, and            H represents a hydrogen atom,        -   each of R¹ to R⁴ independently represents a hydrogen atom or            a C₁-C₂₄ hydrocarbon group which optionally has at least one            functional group selected from the group consisting of a            hydroxyl group, an epoxy group, an amino group, a silanol            group and a C₁-C₂₄ alkoxysilane group,        -   each R⁵ independently represents a C₁-C₄₈ hydrocarbon group            which optionally has at least one functional group selected            from the group consisting of a hydroxyl group, an epoxy            group, an amino group, a silanol group and a C₁-C₂₄            alkoxysilane group, and        -   each R⁶ independently represents a hydrogen atom or a C₁-C₈            alkyl group.

-   4. A method for producing the asphalt composition of any one of    items 1 to 3 above, which comprises:

(1) providing a living block copolymer comprising:

a base block copolymer comprising at least one vinyl aromatic polymerblock (A) composed mainly of vinyl aromatic hydrocarbon monomer unitsand at least one conjugated diene polymer block (B) composed mainly ofconjugated diene monomer units, and

lithium ions bonded to the terminals of the base block copolymer,

(2) reacting the living block copolymer with a modifier compound havingor being capable of forming at least one functional group, to therebyobtain a modified block copolymer, and

(3) adding the obtained modified block copolymer and at least onevulcanizing agent to a molten form of an asphalt while stirring, the atleast one vulcanizing agent being selected from the group consisting ofsulfur and a sulfur-containing compound.

-   5. The method according to item 4 above, wherein the modified block    copolymer obtained in step (2) is subjected to hydrogenation.

Hereinbelow, the present invention is described in detail.

The block copolymer component (I) used in the asphalt composition of thepresent invention comprises at least one modified block copolymercomprising:

a base block copolymer comprising at least one vinyl aromatic polymerblock (A) composed mainly of vinyl aromatic hydrocarbon monomer unitsand at least one conjugated diene polymer block (B) composed mainly ofconjugated diene monomer units, wherein the base block copolymer isunhydrogenated or hydrogenated, and

a modifier group bonded to the base block copolymer, wherein themodifier group has at least one functional group.

The amount of vinyl aromatic hydrocarbon monomer units in the modifiedblock copolymer is generally from 5 to 95% by weight, preferably from 10to 90% by weight, more preferably from 15 to 85% by weight, based on theweight of the modified block copolymer. It is especially recommendedthat the amount of vinyl aromatic hydrocarbon monomer units in themodified block copolymer is from 5 to 60% by weight, preferably from 10to 55% by weight, more preferably from 15 to 50% by weight, based on theweight of the modified block copolymer.

As examples of methods for producing the base block copolymer, there canbe mentioned the methods described in Examined Japanese PatentApplication Publication Nos. Sho 36-19286 (corresponding to GB No.895980), Sho 43-17979 (corresponding to U.S. Pat. No. 4,600,749) and Sho49-36957 (corresponding to U.S. Pat. No. 3,281,383). By any of themethods described in the above-mentioned patent documents, the baseblock copolymer used in the present invention can be produced in theform of a living block copolymer. By a reaction of the living blockcopolymer with the below-described modifier compound, the modified blockcopolymer (having a functional group-containing a modifier group) usedin the present invention, can be obtained. The modified block copolymerused in the present invention has, for example, a structure representedby a formula selected from the group consisting of the followingformulae:(A-B)_(n)-Y, A-(B-A)_(n)-Y, B-(A-B)_(n)-Y, Y-(A-B)_(n), Y-(A-B)_(n)-Y,Y-A-(B-A)_(n)-Y, Y-B-(A-B)_(n)-Y, [(B-A)_(n)]_(m)-Y, [(A-B)_(n)]_(m)-Y,[(B-A)_(n)-B]_(m)-Y, and [(A-B)_(n)-A]_(m)-Y.In the above-mentioned formulae, each A independently represents a vinylaromatic polymer block (A) composed mainly of vinyl aromatic hydrocarbonmonomer units, and each B independently represents a conjugated dienepolymer block (B) composed mainly of conjugated diene monomer units. Itis not necessary that the boundary between the polymer blocks A and B bedistinct. In the above-mentioned formulae, n is an integer of 1 or more,preferably an integer of from 1 to 5, and m is an integer of 2 or more,preferably an integer of from 2 to 11. Each Y independently represents aresidue (i.e., modifier group) of the below-described modifier compoundwhich has or is capable of forming at least one functional group. When Yis bonded to the polymer block A and/or B by the below-described methodincluding a metalation reaction, Y is bonded to a side chain of thepolymer block A and/or polymer block B. The structures of the polymerchains each having Y bonded thereto are the same or different.

In the present invention, a vinyl aromatic polymer block (A) composedmainly of vinyl aromatic hydrocarbon monomer units is a copolymer blockcomprising vinyl aromatic hydrocarbon monomer units and conjugated dienemonomer units or a homopolymer block comprising vinyl aromatichydrocarbon monomer units, wherein the amount of vinyl aromatichydrocarbon monomer units in the copolymer block is 50% by weight ormore, preferably 70% by weight or more, based on the weight of thecopolymer block. A conjugated diene polymer block (B) composed mainly ofconjugated diene monomer units is a copolymer block comprisingconjugated diene monomer units and vinyl aromatic hydrocarbon monomerunits or a homopolymer block comprising conjugated diene monomer units,wherein the amount of conjugated diene monomer units in the copolymerblock is more than 50% by weight, preferably 70% by weight or more,based on the weight of the copolymer block. The vinyl aromatichydrocarbon monomer units may be uniformly distributed or may bedistributed in a tapered configuration in the copolymer block. Thecopolymer block may have a plurality of segments in which the vinylaromatic hydrocarbon monomer units are uniformly distributed, and/or mayhave a plurality of segments in which the vinyl aromatic hydrocarbonmonomer units are distributed in a tapered configuration. Further, thecopolymer block may have a plurality of segments having different vinylaromatic hydrocarbon monomer unit contents. The base block copolymerused in the present invention may be a mixture of a plurality of baseblock copolymers having structures selected from the group consisting ofthe structures represented by the above-mentioned formulae.

When the base block copolymer in the modified block copolymer has atleast one vinyl aromatic hydrocarbon homopolymer block, from theviewpoint of obtaining an asphalt composition having excellentductility, it is preferred that the ratio of the weight of the at leastone vinyl aromatic hydrocarbon homopolymer block to the total weight ofthe vinyl aromatic hydrocarbon monomer units in the base block copolymer(hereinafter referred to as “vinyl aromatic hydrocarbon block ratio”) iscontrolled in the range of from 50% by weight or more, moreadvantageously from 50 to 97% by weight, still more advantageously from60 to 95% by weight. With respect to the weight average molecular weightof the at least one vinyl aromatic hydrocarbon homopolymer block in thebase block copolymer, it is recommended that the weight averagemolecular weight is generally from 5,000 to 500,000, preferably from7,000 to 200,000. The vinyl aromatic hydrocarbon block ratio of the baseblock copolymer can be measured by the following method. The weight ofthe at least one vinyl aromatic hydrocarbon homopolymer block isobtained by, for example, a method in which the unhydrogenated baseblock copolymer is subjected to oxidative degradation using tert-butylhydroperoxide in the presence of osmium tetraoxide as a catalyst (i.e.,the method described in I. M. KOLTHOFF, et al., J. Polym. Sci. 1, 429(1946)). Using the obtained weight of the vinyl aromatic hydrocarbonhomopolymer block, the vinyl aromatic hydrocarbon block ratio of thebase block copolymer is calculated by the below-mentioned formula, withthe proviso that, among the polymer chains (formed by the oxidativedegradation) corresponding to the vinyl aromatic hydrocarbon homopolymerblocks, the polymer chains having a polymerization degree of about 30 orless are not taken into consideration in the measurement of the vinylaromatic hydrocarbon block ratio.Vinyl aromatic hydrocarbon block ratio (% by weight)={(weight of the atleast one vinyl aromatic hydrocarbon homopolymer block in the base blockcopolymer)/(total weight of the vinyl aromatic hydrocarbon monomer unitsin the base block copolymer)}×100.

In the present invention, the microstructure (including the amounts of acis bond, a trans bond, and a vinyl bond) of the conjugated dienemonomer units in the base block copolymer can be appropriatelycontrolled by using the below-described polar compound and the like.When 1,3-butadiene is used as the conjugated diene monomer, the1,2-vinyl bond content is generally in the range of from 5 to 90%,preferably from 10 to 80%. When isoprene or a combination of1,3-butadiene and isoprene is used as the conjugated diene monomer, thetotal content of the 1,2-vinyl bond and 3,4-vinyl bond is generally inthe range of from 3 to 80%, preferably from 5 to 70%. However, in thecase where a hydrogenated block copolymer is used as the base blockcopolymer, the microstructure of the conjugated diene monomer units inthe base block copolymer is controlled to be as follows. When1,3-butadiene is used as the conjugated diene monomer, the 1,2-vinylbond content is preferably in the range of from 10 to 80%, morepreferably from 25 to 75%. When isoprene or a combination of1,3-butadiene and isoprene is used as the conjugated diene monomer, thetotal content of the 1,2-vinyl bond and 3,4-vinyl bond is preferably inthe range of from 5 to 70%.

In the present invention, the conjugated diene monomer is a diolefinhaving a pair of conjugated double bonds. Examples of conjugated dienemonomers include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene),2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene. Of theseconjugated diene monomers, preferred are 1,3-butadiene and isoprene.These conjugated diene monomers can be used individually or incombination.

Examples of vinyl aromatic hydrocarbon monomers include styrene,o-methylstyrene, p-methylstyrene, p-tert-butylstyrene,1,3-dimethylstyrene, α-methyl-styrene, vinylnaphthalene andvinylanthracene. Of these vinyl aromatic hydrocarbon monomers, styreneis preferred. These vinyl aromatic hydrocarbon monomers can be usedindividually or in combination.

In the present invention, a solvent is generally used in the productionof the base block copolymer. Examples of solvents include aliphatichydrocarbons, such as butane, pentane, hexane, isopentane, heptane,octane and isooctane; alicyclic hydrocarbons, such as cyclopentane,methylcyclopentane, cyclohexane, methylcyclohexane and ethylcyclohexane;and aromatic hydrocarbons, such as benzene, toluene, ethylbenzene andxylene. These solvents can be used individually or in combination.

In the production of the base block copolymer, an organolithium compoundis used as a polymerization initiator. The organolithium compound usedin the present invention is an organic compound having at least onelithium atom in a molecule thereof. Examples of organolithium compoundsinclude ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium,sec-butyllithium, tert-butyllithium, hexamethylenedilithium,butadienyldilithium and isoprenyldilithium. Further examples oforganolithium compounds include 1-(t-butoxy)propyllithium which isdescribed in U.S. Pat. No. 5,708,092; a lithium compound which isproduced by reacting 1-(t-butoxy)propyllithium with an isoprene monomerwhich is in an amount of one to several moles per mole of the1-(t-butoxy)propyllithium, wherein the reaction with isoprene isperformed for the purpose of improving the solubility of the1-(t-butoxy)propyllithium; siloxy group-containing alkyllithiums (suchas 1-(t-butyldimethylsiloxy)hexyllithium) which are described in GBPatent No. 2,241,239; aminolithium compounds, such as aminogroup-containing alkyllithiums described in U.S. Pat. No. 5,527,753 anddiisopropylaminolithium. The above-mentioned organolithium compounds canbe used individually or in combination. In the production of the baseblock copolymer, all the amount of the organolithium compound may beadded at one time, or the organolithium compound may be addedportionwise at two or more times.

In the present invention, for controlling the rate of the polymerizationreaction for producing the base block copolymer, for changing themicrostructure of the conjugated diene segments in the base blockcopolymer produced, and for adjusting the reactivity ratio of theconjugated diene monomer to the vinyl aromatic hydrocarbon monomer, apolar compound or a randomizing agent may be used. Examples of polarcompounds and randomizing agents include ethers, amines, thioethers,phosphines, phosphoramides, a potassium salt or sodium of potassium orsodium. Examples of ethers include dimethyl ether, diethyl ether,diphenyl ether, tetrahydrofuran, diethylene glycol dimethyl ether anddiethylene glycol dibutyl ether. Examples of amines include tertiaryamines, such as trimethylamine, triethylamine,tetramethylethylenediamine and cyclic tertiary amines. Examples ofphosphines and phosphoramides include triphenylphosphine andhexamethylphosphoramide.

In the present invention, the reaction temperature for thecopolymerization for producing the base block copolymer is generally inthe range of from −10 to 150° C., preferably from 30 to 120° C. Thereaction time for the copolymerization varies depending on otherconditions, but is generally within 48 hours, preferably from 0.5 to 10hours. It is preferred that the atmosphere of the copolymerizationreaction system is an atmosphere of an inert gas, such as nitrogen gas.With respect to the copolymerization reaction pressure, there is noparticular limitation so long as the pressure is sufficient for themonomers and the solvent to maintain a liquid state. However, thecopolymerization reaction pressure is generally from 0.1 to 3 MPa,preferably from 0.2 to 2 MPa. Further, care must be taken so as toprevent the intrusion of impurities (such as catalyst and/or the livingpolymer, into the copolymerization reaction system.

The modified block copolymer used as the component (I) of the asphaltcomposition of the present invention can be produced, for example, by amethod in which a living block copolymer comprising a base blockcopolymer and lithium ions bonded to the terminals of the base blockcopolymer is produced by a living anionic polymerization, and the livingblock copolymer is reacted with a modifier compound having or beingcapable of forming at least one functional group to obtain a modifiedblock copolymer, optionally followed by partial or completehydrogenation of the obtained modified block copolymer. The functionalgroup of the modifier compound may be protected by a conventionalmethod. As another method for producing the modified block copolymerused as the component (I) of the asphalt composition, there can bementioned a method in which a base block copolymer is reacted with anorganic alkali metal compound (this reaction is called a “metalationreaction”), thereby obtaining a block copolymer having bonded thereto analkali metal, followed by a reaction of the obtained block copolymerwith a modifier compound. In this method, it is preferred that the basereaction and the subsequent reaction of the block copolymer with themodifier compound are performed.

When the base block copolymer is reacted with a modifier compound toobtain a modified block copolymer having a modifier group, it ispossible that a hydroxyl group and an amino group which are contained inthe modifier group are converted to organic alkali metal salts thereof,depending on the type of the modifier compound. In such case, the alkalimetal salts can be reconverted to a hydroxyl group and an amino group byreacting the alkali metal salts with an active hydrogen-containingcompound, such as water or an alcohol.

In the present invention, a modified block copolymer obtained by areaction of the living block copolymer with the modifier compound maycontain an unmodified block copolymer fraction. It is recommended thatthe amount of such unmodified block copolymer fraction in the modifiedblock copolymer is preferably not more than 70% by weight, morepreferably not more than 60% by weight, still more preferably not morethan 50% by weight, based on the weight of the modified block copolymer.

It is preferred that the modifier group bonded to the base blockcopolymer (which is unhydrogenated or hydrogenated) has at least onefunctional group selected from the group consisting of a hydroxyl group,an epoxy group, an amino group, a silanol group and an alkoxysilanegroup. By virtue of any of the above-mentioned functional groups, themodified block copolymer has a high affinity for an asphalt, andinteractions between the modified block copolymer and the asphalt areeffectively caused to occur due to chemical bonds, such as a hydrogenbond between the modified block copolymer and components of the asphalt,thereby exerting the effects aimed at by the present invention.

Examples of modifier groups include those which have at least onefunctional group selected from the group consisting of the functionalgroups represented by the following formulae (1) to (14):

-   -   wherein, in the formulae (1) to (14):        -   N represents a nitrogen atom, Si represents a silicon atom,            O represents an oxygen atom, C represents a carbon atom, and            H represents a hydrogen atom,        -   each of R¹ to R⁴ independently represents a hydrogen atom or            a C₁-C₂₄ hydrocarbon group which optionally has at least one            functional group selected from the group consisting of a            hydroxyl group, an epoxy group, an amino group, a silanol            group and a C₁-C₂₄ alkoxysilane group,        -   each R⁵ independently represents a C₁-C₄₈ hydrocarbon group            which optionally has at least one functional group selected            from the group consisting of a hydroxyl group, an epoxy            group, an amino group, a silanol group and a C₁-C₂₄            alkoxysilane group, and        -   each R⁶ independently represents a hydrogen atom or a C₁-C₈            alkyl group.

As modifier compounds usable for forming at least one of theabove-mentioned modifier groups in the modified block copolymer, therecan be mentioned compounds which have or are capable of forming at leastone of the above-mentioned functional groups. As examples of suchcompounds, there can be mentioned the terminal modifiers described inExamined Japanese Patent Application Publication No. Hei 4-39495(corresponding to U.S. Pat. No. 5,115,035). Specific examples ofmodifier compounds are enumerated below.

Specific examples of modifier compounds having functional groupsrepresented by the formulae (1) to (6) includetetraglycidyl-m-xylene-diamine,tetraglycidyl-1,3-bisaminomethylcyclohexane,tetraglycidyl-p-phenylenediamine, tetraglycidyldiaminodiphenyl-methane,diglycidylaniline, diglycidyl-o-toluidine,N-(1,3-dibutylbutylidene)-3-triethoxysilyl-1-propaneamine,4-di(β-trimethoxysilylethyl)aminostyrene,4-di(β-triethoxysilylethyl)aminostyrene,4-di(γ-tri-methoxysilylpropyl)aminostyrene, and4-di(γ-triethoxysilylpropyl)aminostyrene.

Specific examples of modifier compounds having a functional grouprepresented by the formula (7) include cyclic lactones, such asε-caprolactone, δ-valerolactone, butyrolactone, γ-caprolactone andγ-valerolactone.

Specific examples of modifier compounds having a functional grouprepresented by the formula (8) include 4-methoxybenzophenone,4-ethoxybenzophenone, 4,4′-bis(methoxy)benzophenone,4,4′-bis(ethoxy)benzophenone, γ-glycidoxyethyltrimethoxysilane andγ-glycidoxypropyltrimethoxysilane.

Specific examples of modifier compounds having functional groupsrepresented by the formulae (9) and (10) includeγ-glycidoxybutyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-glycidoxypropyltripropoxysilane and γ-glycidoxypropyltributoxysilane.

Further specific examples of modifier compounds having functional groupsrepresented by the formulae (9) and (10) includeγ-glycidoxypropyltriphenoxysilane,γ-glycidoxypropylmethyldimethoxysilane,γ-glycidoxypropylethyldimethoxysilane,γ-glycidoxypropylethyldiethoxysilane,γ-glycidoxypropylmethyldiethoxysilane,γ-glycidoxypropylmethyldipropoxysilane,γ-glycidoxypropylmethyldibutoxysilane,γ-glycidoxypropylmethyldiphenoxysilane,γ-glycidoxypropyldimethylmethoxysilane,γ-glycidoxypropyldiethylethoxysilane andγ-glycidoxypropyldimethylethoxysilane.

Further specific examples of modifier compounds having functional groupsrepresented by the formulae (9) and (10) also includeγ-glycidoxypropyldimethylphenoxysilane,γ-glycidoxypropyldiethylmethoxysilane,γ-glycidoxypropylmethyldiisopropeneoxysilane,bis(γ-glycidoxypropyl)dimethoxysilane,bis(γ-glycidoxypropyl)diethoxysilane,bis(γ-glycidoxypropyl)dipropoxysilane,bis(γ-glycidoxypropyl)dibutoxysilane,bis(γ-glycidoxypropyl)diphenoxysilane,bis(γ-glycidoxypropyl)methylmethoxysilane andbis(γ-glycidoxypropyl)methylethoxysilane.

Further specific examples of modifier compounds having functional groupsrepresented by the formulae (9) and (10) also includebis(γ-glycidoxypropyl)methylpropoxysilane,bis(γ-glycidoxypropyl)methylbutoxysilane,bis(γ-glycidoxypropyl)methylphenoxysilane,tris(γ-glycidoxypropyl)methoxysilane,γ-methacryloxypropyltrimethoxysilane,γ-methacryloxypropyltriethoxysilane,γ-methacryloxymethyltrimethoxysilane,γ-methacryloxyethyltriethoxysilane,bis(γ-methacryloxypropyl)dimethoxysilane,tris(γ-methacryloxypropyl)methoxysilane,β-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane andβ-(3,4-epoxycyclohexyl)ethyl-triethoxysilane.

Further specific examples of modifier compounds having functional groupsrepresented by the formulae (9) and (10) include:

-   β-(3,4-epoxycyclohexyl)ethyl-tripropoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-tributoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-triphenoxysilane,-   β-(3,4-epoxycyclohexyl)propyl-trimethoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-methyldimethoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-ethyldimethoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-ethyldiethoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-methyldiethoxysilane,-   β-(3,4-epoxycyciohexyl)ethyl-methyldipropoxysilane and-   β-(3,4-epoxycyclohexyl)ethyl-methyldibutoxysilane.

Further specific examples of modifier compounds having functional groupsrepresented by the formulae (9) and (10) also include:

-   β-(3,4-epoxycyclohexyl)ethyl-methyldiphenoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-dimethylmethoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-diethylethoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-dimethylethoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-dimethylpropoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-dimethylbutoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-dimethylphenoxysilane,-   β-(3,4-epoxycyclohexyl)ethyl-diethylmethoxysilane and-   β-(3,4-epoxycyclohexyl)ethyl-methyldiisopropeneoxysilane.

Specific examples of modifier compounds having a functional grouprepresented by the formula (11) include 1,3-dimethyl-2-imidazolidinoneand 1,3-diethyl-2-imidazolidinone.

Specific examples of modifier compounds having a functional grouprepresented by the formula (12) include N,N′-dimethylpropyleneurea andN-methylpyrrolidone.

With respect to the modifier compound used for producing the modifiedblock copolymer, it is preferred that the amount of the modifiercompound is from 0.5 to 5 equivalents, relative to one equivalent of theliving terminals of the base block copolymer. In the present invention,the amount of the living terminals of the base block copolymer can becalculated from the amount of the organolithium compound used in thecopolymerization reaction for producing the base block copolymer.

With respect to the conditions under which the base block copolymer isreacted with the modifier compound, there is no particular limitation.However, the reaction temperature is preferably from 0 to 150° C., morepreferably from 50 to 100° C., and the reaction pressure is preferablyfrom 0 to 10 kg/cm², more preferably from 1 to 5 kg/cm², in terms of thegauge pressure.

A modified block copolymer having bonded thereto a modifier group whichhas a functional group represented by the formula (13) can be obtainedby hydrogenating a modified block copolymer which is obtained using amodifier compound having a functional group represented by the formula(10). A modified block copolymer having bonded thereto a modifier groupwhich has a functional group represented by the formula (14) can beobtained by hydrogenating a modified block copolymer which is obtainedusing a modifier compound having a functional group represented by theformula (11).

By reacting the base block copolymer with the modifier compound, amodified block copolymer can be obtained. With respect to the positionin the base block copolymer at which the modifier group is bonded to thebase block copolymer, there is no particular limitation. However, fromthe viewpoint of obtaining an asphalt composition having excellentproperties at high temperatures, it is preferred that the modifier groupis bonded to a vinyl aromatic polymer block (A) of the base blockcopolymer.

In the present invention, the modified block copolymer containing ahydrogenated base block copolymer can be obtained by partial or completehydrogenation of the above-obtained modified block copolymer. Withrespect to the hydrogenation catalyst, there is no particularlimitation, and any of the conventional hydrogenation catalysts can beused. Examples of hydrogenation catalysts include:

-   (1) a carried, heterogeneous hydrogenation catalyst comprising a    carrier (such as carbon, silica, alumina or diatomaceous earth)    having carried thereon a metal, such as Ni, Pt, Pd or Ru;-   (2) the so-called Ziegler type hydrogenation catalyst which uses a    transition metal salt (such as an organic acid salt or acetylacetone    salt of a metal, such as Ni, Co, Fe or Cr) in combination with a    reducing agent, such as an organoaluminum compound; and-   (3) a homogeneous hydrogenation catalyst, such as the so-called    organometal complex, e.g., an organometal compound containing a    metal, such as Ti, Ru, Rh or Zr. Specific examples of hydrogenation    catalysts include those which are described in Examined Japanese    Patent Application Publication Nos. Sho 42-8704 (corresponding to    Canadian Patent No. 815575), Sho 63-4841 (corresponding to U.S. Pat.    No. 4,501,857) and Hei 1-37970 (corresponding to U.S. Pat. No.    4,673,714). As preferred examples of hydrogenation catalysts, there    can be mentioned a titanocene compound and a mixture of a titanocene    compound and a reductive organometal compound.

Examples of titanocene compounds include those which are described inUnexamined Japanese Patent Application Laid-Open Specification No. Hei8-109219. As specific examples of titanocene compounds, there can bementioned compounds (e.g., biscyclopentadienyltitanium dichloride andmonopentamethylcyclopentadienyltitanium trichloride) which have at leastone ligand having a (substituted) cyclopentadienyl skeleton, an indenylskeleton or a fluorenyl skeleton. Examples of reductive organometalcompounds include organic alkali metal compounds, such as anorganolithium compound; an organomagnesium compound; an organoaluminumcompound; an organoboron compound; and an organozinc compound.

The hydrogenation reaction is performed generally at 0 to 200° C.,preferably at 30 to 150° C. It is recommended that the hydrogen pressurein the hydrogenation reaction is in the range of from 0.1 to 15 MPa,preferably from 0.2 to 10 MPa, more preferably from 0.3 to 5 MPa. Thehydrogenation reaction time is generally in the range of from 3 minutesto 10 hours, preferably from 10 minutes to 5 hours. The hydrogenationreaction may be performed either in a batchwise manner or in acontinuous manner. Further, the hydrogenation reaction may be performedin a manner wherein a batchwise operation and a continuous operation areused in combination.

When the modified block copolymer is subjected to hydrogenation, thereis no particular limitation with respect to the hydrogenation ratio asmeasured with respect to the unsaturated double bonds in the conjugateddiene monomer units, and the hydrogenation ratio can be adjusted to adesired level, depending on the desired properties of the asphaltcomposition. For example, when it is desired to obtain an asphaltcomposition having excellent heat stability, the hydrogenation ratio isgenerally 70% or more, preferably 80% or more, more preferably 90% ormore. Further, when it is desired to obtain an asphalt compositionhaving excellent heat stability without sacrificing the excellentcompatibility between the modified block copolymer and the asphalt, thehydrogenation ratio is preferably from 10% to less than 70%, morepreferably from 15% to less than 65%, still more preferably from 20% toless than 60%.

With respect to the hydrogenation ratio as measured with respect to thevinyl bonds in the conjugated diene monomer units, from the viewpoint ofobtaining an asphalt composition having excellent heat stability, it isrecommended that the hydrogenation ratio is 85% or more, preferably 90%or more, more preferably 95% or more. Herein, the hydrogenation ratiowith respect to the vinyl bonds is the percentage of the number ofhydrogenated vinyl bonds, based on the number of the vinyl bonds (i.e.,the 1,2-vinyl bonds and 3,4-vinyl bonds) in the conjugated diene monomerunits of the base block copolymer prior to hydrogenation.

With respect to the hydrogenation ratio as measured with respect to thearomatic double bonds in the vinyl aromatic hydrocarbon monomer units ofthe base block copolymer, there is no particular limitation. However, itis preferred that the hydrogenation ratio is 50% or less, moreadvantageously 30% or less, still more advantageously 20% or less.

With respect to the modified block copolymer (which is unhydrogenated orhydrogenated) as the component (I) of the asphalt composition of thepresent invention, the weight average molecular weight thereof isgenerally from 30,000 to 1,000,000, preferably from 50,000 to 800,000,more preferably from 70,000 to 600,000. When the weight averagemolecular weight of the modified block copolymer is smaller than 30,000,the asphalt composition has neither a satisfactorily high softeningpoint nor satisfactorily high mechanical strength. On the other hand,when the weight average molecular weight of the modified block copolymeris larger than 1,000,000, the solubility of the modified block copolymerin the asphalt used in the asphalt composition becomes poor.

In the present invention, the amount of vinyl bonds in the conjugateddiene monomer units of a block copolymer can be measured by a methodusing an infrared spectrophotometer (e.g., the Hampton method) or by amethod using a nuclear magnetic resonance (NMR) apparatus. Each of theabove-mentioned hydrogenation ratios can also be measured by a methodusing an infrared spectrophotometer or an NMR apparatus. The weightaverage molecular weight of a block copolymer (such as a modified blockcopolymer) can be measured by gel permeation chromatography (GPC) usinga calibration curve obtained with respect to commercially availablestandard monodisperse polystyrene samples.

By the method described hereinabove, a modified block copolymer (whichis unhydrogenated or hydrogenated) is obtained in the form of a solutionthereof in a solvent. From the obtained solution, the modified blockcopolymer is separated. If desired, before the separation of themodified block copolymer, a catalyst residue may be separated from thesolution. Examples of methods for separating the modified blockcopolymer from the solution include a method in which a polar solvent(which is a poor solvent for the copolymer), such as acetone or analcohol, is added to the solution containing the copolymer, therebyprecipitating the copolymer, followed by recovery of the copolymer; amethod in which the solution containing the copolymer is added to hotwater while stirring, followed by removal of the solvent by steamstripping; and a method in which the solution containing the copolymeris directly heated to evaporate the solvent.

In the present invention, the block copolymer component (I) comprisingat least one modified block Copolymer (which is unhydrogenated orhydrogenated) may have incorporated therein at least one stabilizer.Examples of stabilizers include phenol type stabilizers, phosphorus typestabilizers, sulfur type stabilizers and amine type stabilizers. Theamount of the stabilizer is generally from 0.01 to 5% by weight, basedon the weight of the block copolymer component (I).

Examples of phenol type stabilizers include2,6-di-tert-butyl-4-methylphenol (e.g., “Sumilizer BHT”, manufacturedand sold by Sumitomo Chemical Co., Ltd., Japan),n-octadecyl-3-(4′-hydroxy-3′,5′-di-tert-butylphenyl)propionate (e.g.,“Irganox 1076”, manufactured and sold by Ciba Specialty Chemicals,U.S.A.),tetrakis(methylene-3-(3′,5′-di-tert-butyl-4′-hydroxy-phenyl)propionate)methane(e.g., “Irganox 1010”, manufactured and sold by Ciba SpecialtyChemicals, U.S.A.), and2-tert-butyl-6-(3′-tert-butyl-5′-methyl-2′-hydroxy-benzyl)-4-methylphenylacrylate (e.g., “Sumilizer GM”, manufactured and sold by SumitomoChemical Co., Ltd., Japan). Examples of phosphorus type stabilizersinclude tris(nonylphenyl)phosphite (e.g., “Sumilizer TNP”, manufacturedand sold by Sumitomo Chemical Co., Ltd., Japan) andtris(2,4-di-tert-butylphenyl)phosphite (e.g., “Sumilizer P-16”,manufactured and sold by Sumitomo Chemical Co., Ltd., Japan). Examplesof sulfur type stabilizers include dilauryl thiodipropionate (e.g.,“Sumilizer TPL-R”, manufactured and sold by Sumitomo Chemical Co., Ltd.,Japan) and pentaerythritoltetrakis(β-lauryl)thiopropionate (e.g.,“Sumilizer TP-D”, manufactured and sold by Sumitomo Chemical Co., Ltd.,Japan). Examples of amine type stabilizers include an alkylateddiphenylamine (e.g., “Sumilizer 9A”, manufactured and sold by SumitomoChemical Co., Ltd., Japan), a mixture containingdiallyl-p-phenylenediamine (e.g., “NONFLEX TP-R”, manufactured and soldby Seiko Chemical Co., Ltd., Japan), andN-isopropyl-N′-phenyl-p-phenylenediamine (e.g., “NOCRAC 810-NA”,manufactured and sold by OUCHISHINKO CHEMICAL INDUSTRIAL CO., LTD.,Japan).

In the asphalt composition of the present invention, it is preferredthat the block copolymer component (I) is a mixture of:

10 to 90% by weight of a modified block copolymer (I-A) comprising:

a base block copolymer comprising at least two vinyl aromatic polymerblocks (A) and at least one conjugated diene polymer block (B), and

the modifier group bonded to the base block copolymer,

the base block copolymer being unhydrogenated or hydrogenated; and

90 to 10% by weight of at least one block copolymer selected from thegroup consisting of:

a modified block copolymer (I-B) other than the modified block copolymer(I-A), which comprises:

a base block copolymer comprising at least one vinyl aromatic polymerblock (A) and at least one conjugated diene polymer block (B), and

the modifier group bonded to the base block copolymer,

the base block copolymer being unhydrogenated or hydrogenated, and

an unmodified block copolymer (I-C) comprising at least one vinylaromatic polymer block (A) and at least one conjugated diene polymerblock (B), the unmodified block copolymer (I-C) being unhydrogenated orhydrogenated,

wherein each % by weight is based on the weight of the mixture.

The use of the above-mentioned mixture as the block copolymer component(I) of the asphalt composition, is preferred from the viewpoint ofobtaining the advantage that the asphalt composition of the presentinvention can be used to form a pavement layer having excellent dynamicstability and excellent aggregate-gripping properties. The components(I-A) and (I-B) (which are modified block copolymers) are different fromeach other in the block configuration and/or molecular weight.

With respect to the weight average molecular weights of the components(I-A), (I-B) and (I-C) as measured by GPC using a calibration curveobtained with respect to standard monodisperse polystyrene samples, fromthe viewpoint of obtaining an asphalt composition exhibiting anexcellent balance of the softening point and the anti-phase separationproperty, it is preferred that each of the weight average molecularweights of the components (I-B) and (I-C) is from 30,000 to 200,000,more advantageously from 35,000 to 180,000, still more advantageouslyfrom 40,000 to 150,000, and the weight average molecular weight of thecomponent (I-A) is from 60,000 to 500,000, more advantageously from80,000 to 400,000, still more advantageously from 100,000 to 350,000.

The above-mentioned block copolymer component (I) which is a mixture ofthe component (I-A) and at least one component selected from the groupconsisting of the components (I-B) and (I-C), can be obtained, forexample, by a method in which the above-mentioned components areseparately produced by the above-described conventional method using anorganolithium compound as a polymerization initiator, and the producedcomponents are mixed together. In this method, the weight averagemolecular weights of the components can be adjusted by appropriatelychoosing the amount of the organolithium compound used in the productionof the components. The mixing of the components can be performed, forexample, by the following method. By the above-described conventionalmethod for producing a modified block copolymer, each of the componentsis individually obtained in the form of a solution thereof in a solvent.A deactivating agent (such as water, an alcohol or an acid) is added tothe solutions to deactivate the active species in the solutions. Thethus treated solutions are mixed together in a predetermined ratio. Fromthe resultant mixture is removed the polymerization solvent by steamstripping or the like, followed by drying, thereby obtaining a blockcopolymer mixture as the block copolymer component (I).

Alternatively, the above-mentioned block copolymer component (I) whichis a mixture of different modified block copolymers can also be obtainedby the following method. The polymerization solvents are separated fromthe above-mentioned solutions in which the active species have beendeactivated, to recover the copolymers, followed by drying to obtaindried copolymers. The dried copolymers are mixed together using a rollor the like to obtain a block copolymer mixture as the block copolymercomponent (I).

Further, the block copolymer component (I) which is a mixture of thecomponents (I-A) and (I-B), and the block copolymer component (I) whichis a mixture of the components (I-A) and (I-C) can be produced bymethods other than mentioned above. For example, the block copolymercomponent (I) which is a mixture of the components (I-A) and (I-C) canbe produced, for example, as follows. A living block copolymer havingthe structure of the block copolymer (I-C) is produced in apolymerization reaction system. Then, to the polymerization reactionsystem is added a modifier compound in a predetermined amount (forexample, in an amount of from 0.5 to 5 equivalents, relative to oneequivalent of the living terminals of the living block copolymer),wherein the modifier compound is capable of undergoing a couplingreaction (i.e., there is used a modifier compound having two or morefunctional groups which contribute to a coupling reaction, wherein themodifier compound is selected from the above-mentioned modifiercompounds). By the addition of such modifier compound to thepolymerization reaction system, a part of the living block copolymerchains are caused to be bonded to each other through a residue of themodifier compound, thereby forming the block copolymer (I-A).Thereafter, a deactivating agent, such as an alcohol, is added to thepolymerization reaction system, thereby obtaining a mixture of the blockcopolymers (I-A) and (I-C) in a single polymerization reaction system.On the other hand, the block copolymer component (I) which is a mixtureof the components (I-A) and (I-B) can be produced, for example, asfollows. In a polymerization reaction system, a polymerization reactionis performed in the presence of an organolithium compound as apolymerization initiator to obtain a living block copolymer. Then, theorganolithium compound is further added to the polymerization reactionsystem to continue the polymerization reaction. Thereafter, any of theabove-mentioned modifier compounds is added to the polymerizationreaction system in a predetermined amount (for example, in an amount offrom 0.5 to 5 equivalents, relative to one equivalent of the livingterminals of the living block copolymer), thereby obtaining a mixture ofthe block copolymers (I-A) and (I-B) in a single polymerization reactionsystem.

With respect to the asphalt used as the component (II) of the asphaltcomposition of the present invention, explanations are given below.

Examples of asphalts used in the present invention include a petroleumasphalt (i.e., asphalt by-produced by oil refining), natural asphalt,and mixtures thereof with petroleum. Each of the above-mentionedasphalts contains bitumen as the main component thereof. Specificexamples of asphalts include a straight asphalt, a semi-blown asphalt, ablown asphalt, tar, pitch, a cutback asphalt (i.e., a mixture of asphaltwith oil), and an asphalt emulsion. These asphalts can be usedindividually or in combination. In the present invention, as a preferredasphalt, there can be mentioned a straight asphalt having a penetrationratio of from 30 to 300, preferably from 40 to 200, more preferably from45 to 150, wherein the penetration ratio of the asphalt is measured inaccordance with JIS K 2207. The amount of the block copolymer component(I) contained in the asphalt composition of the present invention isfrom 0.5 to 50 parts by weight, preferably from 1 to 30 parts by weight,more preferably from 3 to 20 parts by weight, relative to 100 parts byweight of the asphalt (II).

With respect to the at least one vulcanizing agent (which is selectedfrom the group consisting of sulfur and a sulfur-containing compound)used as the component (III) of the asphalt composition of the presentinvention, explanations are given below.

Examples of sulfur products used as the vulcanizing agent (III) includea powdery sulfur, a precipitated sulfur, a colloidal sulfur, asurface-treated sulfur, an insoluble sulfur and an inert sulfur.Examples of sulfur-containing compounds used as the vulcanizing agent(III) include sulfur chloride, sulfur dioxide, morpholine disulfide, analkylphenol disulfide and a high molecular weight polysulfide. Acrosslinking accelerator can be used in an appropriate amount incombination with the vulcanizing agent (III). Examples of crosslinkingaccelerators include a sulfenamide type accelerator, a guanidine typeaccelerator, a thiuram type accelerator, an aldehyde-amine typeaccelerator, an aldehyde-ammonia type accelerator, a thiazole typeaccelerator, a thiourea type accelerator, a dithiocarbamate typeaccelerator and a xanthate type accelerator. Specific examples of suchcrosslinking accelerators include a diphenylguanidine, n-butylaldehyde-anil condensate, a hexamethylenetetramine,2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazyl sulfenamide,thiocarbanilide, tetramethylthiuram monosulfide, sodium dimethyldithiocarbamate and zinc isopropyl xanthogenate. The amount of thevulcanizing agent as the component (III) is in the range of from 0.01 to10 parts by weight, preferably from 0.02 to 5 parts by weight, morepreferably from 0.05 to 2 parts by weight, relative to 100 parts byweight of the asphalt as the component (II). The amount of thecrosslinking accelerator is generally in the range of from 0.01 to 10parts by weight, preferably from 0.02 to 5 parts by weight, morepreferably from 0.05 to 2 parts by weight, relative to 100 parts byweight of the asphalt as the component (II). By using the components(I), (II) and (III) and optionally a crosslinking accelerator in theamounts within the above-mentioned ranges, the effects of the presentinvention can be exerted at a maximum level.

The asphalt composition of the present invention may contain a silanecoupling agent. Specific examples of silane coupling agents includebis[3-(triethoxysilyl)propyl]tetrasulfide,bis[3-(triethoxysilyl)propyl]disulfide,bis[2-(triethoxysilyl)ethyl]-tetrasulfide,3-mercaptopropyl-trimethoxysilane,3-mercaptopropyl-methyldimethoxysilane,3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide,3-triethoxysilylpropylbenzothiazoletetrasulfide, vinyltrimethoxysilane,vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane,p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane,3-methacryloxypropyltrimethoxysilane,3-methacryloxypropylmethyldiethoxysilane,3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane,N-2(aminoethyl)3-aminopropylmethyldimethoxysilane,N-2(aminoethyl)3-aminopropyltrimethoxysilane,N-2(aminoethyl)3-aminopropyltriethoxysilane,3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine,N-phenyl-3-aminopropyltrimethoxysilane and3-isocyanatepropyltriethoxysilane.

As a preferred example of the silane coupling agent, there can bementioned a compound having a polysulfide linkage containing a silanolgroup or an alkoxysilane in combination with two or more sulfur atoms,wherein any of the sulfur atoms may be present in the form of a mercaptogroup. Specific examples of such preferred silane coupling agentsinclude bis[3-(triethoxysilyl)propyl]tetrasulfide,bis[3-(triethoxysilyl)propyl]disulfide,bis[2-(triethoxysilyl)ethyl]-tetrasulfide,3-mercaptopropyl-trimethoxysilane,3-mercaptopropyl-methyldimethoxysilane,3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide and3-triethoxysilylpropylbenzothiazoletetrasulfide. It is recommended thatthe amount of the silane coupling agent is from 0.01 to 20 parts byweight, preferably from 0.05 to 10 parts by weight, more preferably from0.1 to 5 parts by weight, relative to 100 parts by weight of the asphaltas the component (II).

From the viewpoint of obtaining excellent aggregate-gripping properties,the asphalt composition of the present invention may contain asurfactant, such as an anionic surfactant, a cationic surfactant or anonionic surfactant. Specific examples of surfactants include a higherfatty acid having 11 or more carbon atoms (e.g., stearic acid, oleicacid, linoleic acid or linolenic acid) and a metal salt thereof, amonoamine, a diamine, a polyamine and a co-oligomer of polyethyleneoxide and polypropylene oxide. Further examples of surfactants includean acidic, organic phosphate compound; a mixture of an acidic, organicphosphate compound and an inorganic phosphate compound; a polycarboxylicacid and an anhydride thereof; an aliphatic phosphate; a phosphoric acidester with a higher alcohol (e.g., stearyl phosphate); a mixture of ahigher alcohol and a phosphorylated alcohol; gallic acid and derivativesthereof; fatty acids derived from a tall oil, and derivatives thereof; acondensate of polyalkylenepolyamine and a fatty acid; a liquid epoxy; agraft-modified polyethylene obtained by grafting maleic anhydride ontopolyethylene; a graft-modified polypropylene obtained by grafting maleicanhydride onto polypropylene; a graft-modified styrene/butadiene blockcopolymer obtained by grafting maleic anhydride onto a styrene/butadieneblock copolymer, and a hydrogenation product thereof; and ahydrogenation product of a graft-modified styrene/isoprene blockcopolymer which is obtained by grafting maleic anhydride onto astyrene/isoprene block copolymer.

If desired, the asphalt composition of the present invention may containany of the conventional additives. With respect to the type of theadditive, there is no particular limitation so long as it is an additivewhich is generally used in combination with a thermoplastic resin or arubbery copolymer. Examples of additives include those which aredescribed in “Gomu Purasuchikku Haigou Yakuhin (Additives for Rubber andPlastic)” (published by Rubber Digest Co., Ltd., Japan (1968)). Specificexamples of additives include inorganic fillers, such as calciumcarbonate, magnesium carbonate, magnesium hydroxide, calcium sulfate,barium sulfate, silica, clay, talc, mica, wollastonite, montmorillonite,zeolite, alumina, titanium oxide, magnesium oxide, zinc oxide, a slagwool and a glass fiber; pigments, such as carbon black and an ironoxide; lubricants, such as stearic acid, behenic acid, zinc stearate,calcium stearate, magnesium stearate and ethylenebisstearoamide; moldrelease agents; softening agents and plasticizers, such as a paraffinicprocess oil, a naphthenic process oil, an aromatic process oil, aparaffin, an organic polysiloxane and a mineral oil; antioxidants, suchas a hindered phenol type antioxidant and a phosphorus type thermalstabilizer; hindered amine type light stabilizers; benzotriazole typeultraviolet absorbers; flame retardants; antistatic agents; reinforcingagents, such as an organic fiber, a glass fiber, a carbon fiber and ametal whisker; coloring agents; and mixtures thereof. With respect tothe amount of the additive, there is no particular limitation; however,the amount of the additive is generally 50 parts by weight or less,relative to 100 parts by weight of the modified block copolymer.

With respect to the method for producing the asphalt composition of thepresent invention, there is no particular limitation. For example, theasphalt composition can be produced by a method which comprises:

(1) providing a living block copolymer comprising:

a base block copolymer comprising at least one vinyl aromatic polymerblock (A) composed mainly of vinyl aromatic hydrocarbon monomer unitsand at least one conjugated diene polymer block (B) composed mainly ofconjugated diene monomer units, and

lithium ions bonded to the terminals of the base block copolymer,

(2) reacting the living block copolymer with a modifier compound havingor being capable of forming at least one functional group, to therebyobtain a modified block copolymer, and

(3) adding the obtained modified block copolymer and at least onevulcanizing agent to the molten form of an asphalt while stirring, theat least one vulcanizing agent being selected from the group consistingof sulfur and a sulfur-containing compound.

With respect to the substances used in the method for producing theasphalt composition (i.e., the living block copolymer, the modifiercompound, the vulcanizing agent, the asphalt and the like), the methodsfor producing the substances and the types and amounts of the substancesare as described above in connection with the asphalt composition of thepresent invention.

With respect to the conditions under which a mixture of the modifiedblock copolymer, the vulcanizing agent and the asphalt is stirred, thereis no particular limitation. However, the stirring temperature ispreferably in the range of from 160 to 200° C., more preferably about180° C., and the stirring time is preferably in the range of from 30minutes to 6 hours, more preferably from 2 to 3 hours. Further, thestirring rate varies depending on the apparatus used, but is generallyfrom 100 to 8,000 rpm.

If desired, the modified block copolymer obtained in the above-mentionedstep (2) may be subjected to hydrogenation. The method for hydrogenationis as described above in connection with the asphalt composition of thepresent invention.

The asphalt composition of the present invention can be advantageouslyused in road paving. Especially, by virtue of the excellent propertiesof the asphalt composition with respect to dynamic stability andaggregate-gripping properties, the asphalt composition of the presentinvention can be advantageously used as a binder for a drainage pavementfor various roads, such as a road having a large traffic, an expressway,and a road segment at which the load of traffic tends to concentrate(e.g., an intersection or a curving road).

A drainage pavement comprises a road and, formed thereon, a drainagepavement layer having a plurality of voids for drainage, wherein thedrainage pavement layer is an asphalt mixture comprised of a pluralityof aggregates and an asphalt composition as a binder.

When the asphalt composition of the present invention is used as abinder in a drainage pavement, the drainage pavement exhibits excellentproperties with respect to, e.g., rutting resistance, waterpermeability, traffic noise reduction properties and low-temperatureproperties (e.g., crack resistance at low temperatures). The asphaltcomposition of the present invention can also be used for forming apermeable pavement, which is required to have the same functions asthose of a drainage pavement.

Generally, an asphalt pavement is formed by the following method. To amixture of a coarse aggregate (e.g., crushed stone), a fine aggregate(e.g., sand or crushed sand), stone dust and the like (wherein themixture has an appropriate range of particle size distribution) is addedan asphalt composition (as a binder) which is heated, thereby obtainingan asphalt mixture. The obtained asphalt mixture is spread over a road,and the resultant asphalt mixture layer on the road is rolled flat byusing a roller or the like, thereby obtaining an asphalt pavement. Thedrainage pavement layer of a drainage pavement has an extremely largenumber of intercommunicating voids for drainage, as compared to thenumber of voids in the pavement layer of a conventional pavementproduced using a conventional asphalt mixture. By virtue of suchproperty, the drainage pavement exhibits excellent functions, e.g., thedrainability for preventing the occurrence of rain pools, the ability toensure safe driving by preventing a continuous water thin layer frombeing formed by rain on the road, and the ability to reduce trafficnoise (e.g., an exhaust noise or a noise caused by the contact betweenrotating tires and the road surface). The asphalt composition of thepresent invention can be advantageously used for forming a drainagepavement wherein the drainage pavement layer has a void ratio of from 5to 35%, preferably from 10 to 30%, more preferably from 12 to 28%.

The void ratio of a drainage pavement layer is defined by the followingformula:

${{Void}\mspace{14mu}{{ratio}(\%)}} = {{\frac{V_{v}}{V} \times 100} = {\lbrack {1 - \frac{\rho_{m}}{D}} \rbrack \times 100}}$wherein:

ρ_(m) represents the density (g/cm³) of the asphalt mixture (which iscomprised of a plurality of aggregates and an asphalt composition),

V represents the volume (cm³) of the asphalt mixture,

V_(v) represents the void volume (cm³) of the asphalt mixture, and

D represents the theoretical maximum density (g/cm³) of the asphaltmixture.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in more detail withreference to the following Examples and Comparative Examples, whichshould not be construed as limiting the scope of the present invention.

The properties of unhydrogenated or hydrogenated block copolymers and ofasphalt compositions were determined by the following methods.

-   1. Properties of Block Copolymers (Such as Modified Block    Copolymers)    (1) Styrene Content:

The absorption intensity of a block copolymer at 262 nm was measuredusing an ultraviolet spectrophotometer (trade name: UV200; manufacturedand sold by Hitachi, Ltd., Japan), and the styrene content wascalculated therefrom.

(2) Vinyl Bond Content and Hydrogenation Ratio:

The vinyl bond content and hydrogenation ratio were measured by means ofa nuclear magnetic resonance (NMR) apparatus (trade name: DPX-400;manufactured and sold by BRUKER, Germany).

(3) Weight Average Molecular Weight:

The weight average molecular weight was measured by gel permeationchromatography (GPC) using a GPC apparatus (manufactured and sold byWaters Corporation, U.S.A.) and a column packed with a polystyrene gel(Shodex, manufactured and sold by Showa Denko Co., Japan), underconditions wherein tetrahydrofuran was used as a solvent and themeasuring temperature was 35° C. In the measurement of the weightaverage molecular weight, there was used a calibration curve obtainedwith respect to commercially available standard monodisperse polystyrenesamples.

(4) Amount of the Unmodified Block Copolymer Fraction in a ModifiedBlock Copolymer:

A sample solution was prepared by mixing together 20 ml oftetrahydrofuran, 10 mg of the modified block copolymer and 10 mg of alow molecular weight internal standard polystyrene having a weightaverage molecular weight of 8,000. The sample solution was subjected togel permeation chromatography (GPC) in substantially the same manner asin item (3) above, thereby obtaining a chromatogram. From thechromatogram, the ratio (a) of the peak area of the modified blockcopolymer to the peak area of the internal standard polystyrene wasdetermined. On the other hand, the same sample solution as mentionedabove was subjected to gel permeation chromatography (GPC) insubstantially the same manner as in item (3) above, except that therewere used a GPC apparatus (Zorbax, manufactured and sold by DuPont,U.S.A) and a column packed with a silica gel. The silica gel adsorbs themodified block copolymer fraction but does not adsorb the unmodifiedblock copolymer fraction. From the resultant chromatogram, the ratio (b)of the peak area of the block copolymer (i.e., unmodified blockcopolymer fraction) to the peak area of the internal standardpolystyrene was determined.

The ratio (a) reflects the total peak area ascribed to both theunmodified block copolymer fraction and the modified block copolymerfraction, and the ratio (b) reflects the peak area ascribed to only theunmodified block copolymer fraction. Therefore, from the ratio (a) andthe ratio (b), the amount of the unmodified block copolymer fraction inthe modified block copolymer was obtained.

-   2. Production of Block Copolymers (Such as Modified Block    Copolymers)

The hydrogenation catalyst used in hydrogenation reactions was preparedby the following method.

A reaction vessel was purged with nitrogen. To the reaction vessel wereadded two liters of dried, purified cyclohexane. Then, 40 mmol ofbis(η⁵-cyclopentadienyl)titaniumdi(p-tolyl) and 150 g of a1,2-polybutadiene having a weight average molecular weight of about1,000 and a 1,2-vinyl bond content of about 85% were added to anddissolved in the cyclohexane, thereby obtaining a solution. Acyclohexane solution of 60 mmol of n-butyllithium was added to thesolution in the reaction vessel, and a reaction was performed at roomtemperature for 5 minutes, and then 40 mmol of n-butanol was immediatelyadded to the reaction vessel while stirring, thereby obtaining ahydrogenation catalyst. The obtained hydrogenation catalyst waspreserved at room temperature.

a. Polymer 1

An autoclave equipped with a stirrer and a jacket was washed, dried andpurged with nitrogen. To the autoclave was added a cyclohexane solutionof 15 parts by weight of purified styrene (styrene concentration: 20% byweight). Tetramethylethylenediamine and, then, n-butyllithium were addedto the autoclave, wherein the amount of the tetramethylethylenediaminewas 0.1 mole per mole of the n-butyllithium, and the amount of then-butyllithium was 0.135 part by weight, relative to 100 parts by weightof the total of the monomers used in the production of the polymer 1.Then, a polymerization reaction was performed at 70° C. for 1 hour.Subsequently, a cyclohexane solution of 70 parts by weight of purifiedbutadiene (butadiene concentration: 20% by weight) was added to theautoclave, and a polymerization reaction was performed at 70° C. for 1hour. Thereafter, a cyclohexane solution of 15 parts by weight ofpurified styrene was added to the autoclave, and a polymerizationreaction was performed at 70° C. for 1 hour, thereby obtaining a livingblock copolymer.

The obtained living block copolymer was reacted with1,3-dimethyl-2-imidazolidinone as a modifier compound (hereinafter, thismodifier compound is referred to as “modifier compound M1”), wherein themodifier compound was used in an amount equimolar to the n-butyllithiumwhich was used above. To the resultant reaction mixture were addedmethanol and, then,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate as a stabilizerwherein the amount of the stabilizer was 0.3 part by weight, relative to100 parts by weight of the above-obtained living block copolymer,thereby obtaining a modified block copolymer (polymer 1).

The obtained polymer 1 had a styrene content of 30% by weight, a styreneblock ratio of 95% by weight, a vinyl bond content of 15%, and a weightaverage molecular weight of 110,000. Further, the amount of theunmodified block copolymer fraction in the polymer 1 was 25% by weight,based on the weight of the polymer 1.

b. Polymer 2

Substantially the same procedure as in the production of the polymer 1was repeated except that no modifier compound was used, therebyobtaining an unmodified block copolymer (polymer 2).

c. Polymer 3

An autoclave equipped with a stirrer and a jacket was washed, dried andpurged with nitrogen. To the autoclave was added a cyclohexane solutionof 30 parts by weight of purified styrene (styrene concentration: 20% byweight). Tetramethylethylenediamine and, then, n-butyllithium were addedto the autoclave, wherein the amount of the tetramethylethylenediaminewas 0.1 mol per mol of the n-butyllithium, and the amount of then-butyllithium was 0.1 part by weight, relative to 100 parts by weightof the total of the monomers used in the production of the polymer 3.Then, a polymerization reaction was performed at 70° C. for 1 hour.Subsequently, a cyclohexane solution of 70 parts by weight of purifiedbutadiene (butadiene concentration: 20% by weight) was added to theautoclave, and a polymerization reaction was performed at 70° C. for 1hour, thereby obtaining a living block copolymer.

The obtained living block copolymer was reacted withtetraglycidyl-1,3-bisaminomethylcyclohexane as a modifier compound(hereinafter, this modifier compound is referred to as “modifiercompound M2”), wherein the modifier compound was used in an amount of ¼mole, relative to the mole of the n-butyllithium which was used above.To the resultant reaction mixture were added methanol and, then,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate as a stabilizerwherein the amount of the stabilizer was 0.3 part by weight, relative to100 parts by weight of the above-obtained living block copolymer,thereby obtaining a modified block copolymer (polymer 3).

The obtained polymer 3 had a styrene content of 30% by weight, a styreneblock ratio of 100% by weight, a vinyl bond content of 17%, and a weightaverage molecular weight of 440,000. Further, the amount of theunmodified block copolymer fraction in the polymer 3 was 30% by weight,based on the weight of the polymer 3.

d. Polymer 4

A modified block copolymer in the form of a solution thereof wasproduced in substantially the same manner as in the production of thepolymer 1, except that the amount of tetramethylethylenediamine waschanged so that the modified block copolymer had a vinyl bond content of35%. To the solution of the modified block copolymer was added theabove-mentioned hydrogenation catalyst in an amount of 100 ppm byweight, in terms of the amount of titanium, based on the weight of themodified block copolymer, and a hydrogenation reaction was performedunder conditions wherein the hydrogen pressure was 0.7 MPa and thetemperature was 65° C. After completion of the hydrogenation reaction,methanol was added to the resultant reaction mixture, followed byaddition of, as a stabilizer,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate in an amount of0.3 part by weight, relative to 100 parts by weight of the modifiedblock copolymer, thereby obtaining a hydrogenated, modified blockcopolymer (polymer 4).

The obtained polymer 4 had a hydrogenation ratio of 98%. Further, theamount of the unmodified block copolymer fraction in the polymer 4 was30% by weight, based on the weight of the polymer 4.

e. Polymer 5

A living block copolymer was produced in substantially the same manneras in the production of the polymer 1. To the produced living blockcopolymer was added γ-glycidoxypropyltriethoxysilane as a modifiercompound (hereinafter, this modifier compound is referred to as“modifier compound M3”) in an amount equimolar to the n-butyllithiumused in the production of the living block copolymer, thereby obtaininga modified block copolymer in the form of a solution thereof.

To the solution of the modified block copolymer was added theabove-mentioned hydrogenation catalyst in an amount of 100 ppm byweight, in terms of the amount of titanium, based on the weight of themodified block copolymer, and a hydrogenation reaction was performedunder conditions wherein the hydrogen pressure was 0.7 MPa and thetemperature was 65° C., thereby obtaining a reaction mixture containinga hydrogenated, modified block copolymer (polymer 5) having ahydrogenation ratio of about 35%. After completion of the hydrogenationreaction, methanol was added to the reaction mixture, followed byaddition of, as a stabilizer,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate in an amount of0.3 part by weight, relative to 100 parts by weight of the modifiedblock copolymer. The amount of the unmodified block copolymer fractionin the polymer 5 was 30% by weight, based on the weight of the polymer5.

f. Polymer 6

An autoclave equipped with a stirrer and a jacket was washed, dried andpurged with nitrogen. To the autoclave was added a cyclohexane solutionof 19 parts by weight of purified styrene (styrene concentration: 20% byweight). Tetramethylethylenediamine and, then, n-butyllithium were addedto the autoclave, wherein the amount of the tetramethylethylenediaminewas 0.1 mole per mole of the n-butyllithium, and the amount of then-butyllithium was 0.079 part by weight, relative to 100 parts by weightof the total of the monomers used in the production of the polymer 6.Then, a polymerization reaction was performed at 70° C. for 1 hour.Subsequently, a cyclohexane solution of 45 parts by weight of purifiedbutadiene (butadiene concentration: 20% by weight) was added to theautoclave, and a polymerization reaction was performed at 70° C. for 1hour. Thereafter, to the autoclave was added n-butyllithium in an amountof 0.043 part by weight, relative to 100 parts by weight of the total ofthe monomers used in the production of the polymer 6. Then, to theautoclave was added a cyclohexane solution of 25 parts by weight ofpurified butadiene (butadiene concentration: 20% by weight), and apolymerization reaction was performed at 70° C. for 1 hour. Further, acyclohexane solution of 11 parts by weight of purified styrene (styreneconcentration: 20% by weight) was added to the autoclave, and apolymerization reaction was performed at 70° C. for 1 hour, therebyobtaining a living block copolymer.

The obtained living block copolymer was reacted with the above-mentionedmodifier compound M1, wherein the modifier compound Ml was used in anamount equimolar to all of the n-butyllithium which was used above inthe production of the living block copolymer. To the resultant reactionmixture were added methanol and, then,octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate as a stabilizerin an amount of 0.3 part by weight, relative to 100 parts by weight ofthe living block copolymer, thereby obtaining a modified block copolymer(polymer 6).

The obtained polymer 6 had a styrene content of 30% by weight, a styreneblock ratio of 94% by weight, and a vinyl bond content of 15%. Also, thepolymer 6 was comprised of 74 parts by weight of a fraction having apeak molecular weight of 153,000 and 26 parts by weights of a fractionhaving a peak molecular weight of 65,000, wherein the peak molecularweights were as measured by GPC using a calibration curve obtained withrespect to standard monodisperse polystyrene samples. Further, theamount of the unmodified block copolymer fraction in the polymer 6 was30% by weight, based on the weight of the polymer 6.

g. Polymer 7

Substantially the same procedure as in the production of the polymer 6was repeated except that no modifier compound was used, therebyobtaining an unmodified block copolymer (polymer 7).

-   3. Production of Asphalt Compositions

400 g of straight asphalt 60-80 (manufactured and sold by NIPPON OILCOMPANY, LIMITED, Japan) was added to a metal can having a volume of 750ml. The metal can containing the straight asphalt was put into an oilbath having a temperature of 180° C. so that the straight asphalt wassatisfactorily heated, thereby melting the asphalt. Then, to theresultant molten asphalt were added a predetermined amount of a blockcopolymer and optionally a predetermined amount of sulfur bit by bitwhile stirring. After completion of the addition of a block copolymerand optional sulfur, the resultant mixture was stirred at a revolutionrate of 5,000 rpm for 90 minutes, thereby obtaining an asphaltcomposition.

-   4. Properties of Asphalt Compositions    (1) Softening Point (Ring-and-Ball Method)

The softening point of the asphalt composition was measured inaccordance with JIS K 2207. Specifically, the ring of a ring-and-ballapparatus as defined in JIS K 2207 is filled with a sample of theasphalt composition. The ring-and-ball apparatus is immersed inglycerol, and the ring is maintained level in the glycerol. Then, a ballhaving a weight of 3.5 g is placed at the center of the ring filled withthe sample. The temperature of the glycerol is elevated at a rate of 5°C./min, so as to soften the sample gradually. The central portion of thesoftening sample is gradually sagged under the weight of the ball, andthe temperature (softening point) at which the sagged central portion ofthe sample reaches a bottom plate placed below the ring is measured.

(2) Melt Viscosity

The melt viscosity was measured by means of a Brookfield viscometer at180° C.

(3) Penetration Ratio

The penetration ratio of the asphalt composition was measured inaccordance with JIS K 2207. Specifically, a sample of the asphaltcomposition is placed in a thermostatic water bath, and the temperatureof the sample is maintained at 25° C. Then, a prescribed needle iscaused to penetrate into the sample for 5 seconds. The distance overwhich the needle has penetrated into the sample is measured, and isdefined as the penetration ratio.

(4) Elongation

The elongation of the asphalt composition was measured in accordancewith JIS K 2207. Specifically, a sample of the asphalt composition ispoured into a mold to shape the sample into a prescribed-form. Then, theshaped sample is placed in a thermostatic water bath, and thetemperature of the sample is maintained at 4° C. Then, the sample ispulled at a rate of 5 cm/min until it is broken, and the elongation ofthe sample at the time of breakage is measured.

(5) Adhesion Strength

The adhesion strength of the asphalt composition was measured by thefollowing method. The asphalt composition is dissolved in toluene, andthe resultant solution is coated onto a canvas using a coater. Thecoated canvas is dried, first at room temperature for 1 hour, and thenat 70° C. in an oven for 7 minutes, thereby completely evaporating thetoluene from the coated canvas. Subsequently, the coated canvas isplaced in an oven together with a granite (as an adherend) having asmooth surface, and the coated canvas and the granite are heated at 70°C. for 1 hour. Then, the coated canvas and the granite are taken outfrom the oven and rapidly pressed onto each other twice using a rollerunder a load of 1 kg, thereby adhering the coated canvas onto thegranite. The resultant structure in which the coated canvas is adheredonto the granite, is placed in a thermostatic chamber at a temperatureof 23° C., and a peeling test (peeling angle: 180°) in which the canvasis peeled off from the granite is performed to measure the adhesionstrength of the asphalt composition.

(6) Flexural Properties at Low Temperatures

The flexural stress of the asphalt composition was measured by thefollowing method. The asphalt composition is poured into a mold having asize of 20 mm×20 mm×120 mm, and the excess asphalt composition (i.e.,the portion of the asphalt composition which is above the upper end ofthe mold) is cut off. The mold containing the asphalt composition isplaced in a cryostat, and the asphalt composition in the mold ismaintained at −20° C. for 4 hours or more. Then, the resultant moldedproduct of the asphalt composition is rapidly taken out from the mold,and is measured with respect to the flexural stress by a method in whichthe molded product is supported at two points thereof which are at adistance (span) of 80 mm from each other, and a load is applied, at aloading rate of 100 mm/min, to a portion of the molded product which isat a middle of the 80 mm span.

(7) High-Temperature Storage Stability

The high temperature storage stability of the asphalt composition wasevaluated by the following method. An aluminum can having an innerdiameter of 50 mm and a height of 130 mm is filled up with the asphaltcomposition immediately after the production thereof. The aluminum cancontaining the asphalt composition is placed in an oven and heated at180° C. for 24 hours. The aluminum can is taken out from the oven andallowed to stand so that the asphalt composition in the aluminum cancools to room temperature. As samples, upper and lower portions of theresultant solidified asphalt composition, which are a 4 cm-thick lowerlayer at a lower end portion and a 4 cm-thick upper layer at an upperend portion, are taken by cutting. The softening points of both thesamples are measured. The difference in softening point between thesamples is used as a yardstick for the high temperature storagestability of the asphalt composition.

-   5. Properties of a Drainage Pavement Mixture

An aggregate comprising approximately 85% by weight of crushed stone No.6, approximately 10% by weight of crushed sand and approximately 5% byweight of stone dust was produced, wherein the composition of theaggregate was chosen so as to have a void ratio of approximately 20%.The aggregate was heated to 170° C. To the heated aggregate was added 5%by weight, based on the weight of the aggregate, of a molten form of anasphalt composition (as a binder), followed by mixing well at 170° C.,thereby obtaining a drainage pavement mixture having a void ratio ofapproximately 20%. With respect to the obtained mixture, thebelow-mentioned properties were measured.

(1) Wheel Tracking Test (Yardstick for Dynamic Stability)

The wheel tracking test for evaluating the dynamic stability of thedrainage pavement mixture was performed in accordance with the methoddescribed in “Hosou Shikenhou Binran Bessatsu (Zantei Shikenhouhou)(Handbook of Pavement Test Method: separate volume (interim testmethod)”, published by the Japan Road Association Corporation, Japan.The test was performed at 60±0.5° C.

(2) Cantabro Test (Yardstick for Aggregate-Gripping Properties)

The Cantabro test for measuring the Cantabro loss ratio of the drainagepavement mixture was performed in accordance with the method describedin “Hosou Shikenhou Binran Bessatsu (Zantei Shikenhouhou) (Handbook ofPavement Test Method: separate volume (interim test method)”, publishedby the Japan Road Association Corporation, Japan. The curing of thedrainage pavement mixture was performed at 0° C. and the test wasperformed at 18° C.

EXAMPLES 1 TO 3 AND COMPARATIVE EXAMPLES 1 TO 5

Asphalt compositions were produced in accordance with the formulationsindicated in Table 1 (the polymer 1 or 2 was used as a block copolymer).Specifically, the production of each asphalt composition was performedas follows.

400 g of straight asphalt 60-80 (manufactured and sold by NIPPON OILCOMPANY, LIMITED, Japan) was added to a metal can having a volume of 750ml. The metal can containing the straight asphalt was put into an oilbath having a temperature of 180° C. so that the straight asphalt wassatisfactorily heated, thereby melting the asphalt. Then, to theresultant molten asphalt were added a predetermined amount of a blockcopolymer and optionally a predetermined amount of sulfur (trade name:GOLDEN FLOWER SULFUR POWDER; manufactured and sold by Tsurumi ChemicalCo., Japan) bit by bit while stirring. After completion of the additionof a block copolymer and optional sulfur, the resultant mixture wasstirred at a revolution rate of 5,000 rpm for 90 minutes, therebyobtaining an asphalt composition. The properties of the obtained asphaltcomposition are shown in Table 1.

TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Comp. Ex. 2 Ex. 3 CompEx. 4 Ex. 5 Block copolymer Polymer 1 Polymer 1 Polymer 1 Polymer 1Polymer 1 Polymer 1 Polymer 1 Polymer 2 Amount of block copolymer 8 3 200.3 60 8 8 8 (parts by weight) Amount of asphalt 100 100 100 100 100 100100 100 (parts by weight) Amount of sulfur 0.2 4 0.05 5 0.2 0 12 0.2(parts by weight) Softening point (° C.) 95 87 99 54 Not measurable 84Not measurable 85 Melt viscosity (cP) 580 420 595 250 due to 410 due to460 Penetration ratio (1/10 mm) 40 42 57 58 high viscosity 35 highviscosity 40 Elongation (cm) 81 80 88 12 92 75 Adhesion strength 4,8004,010 5,200 150 2,920 3,200 (gf/10 mm) Flexural stress (N/mm²) 10.7 9.212.8 3.6 8.2 8.7 High temperature Difference 17 17 20 10 Not measurable22 Not measurable 23 storage in softening due to due to stability point(° C.) high viscosity high viscosity

Using individually the asphalt compositions produced in Example 1,Comparative Example 3 and Comparative Example 5, drainage pavementmixtures were produced. The properties of the drainage pavement mixturesare shown in Table 2 below.

As seen from Table 2, a drainage pavement mixture produced using theasphalt composition of the present invention exhibits excellent dynamicstability and excellent aggregate-gripping properties. Therefore, theasphalt composition of the present invention can be advantageously usedfor forming an asphalt pavement.

TABLE 2 Comparative Comparative Example 1 Example 3 Example 5 PropertiesDynamic 10,400 8,200 8,200 of stability drainage (pass/mm) pavementCantabro 12 18 22 mixture loss ratio (%)

EXAMPLES 4 TO 6

Drainage pavement mixtures were produced in substantially the samemanner as in Example 1, except that, in stead of the polymer 1, thepolymers 3, 4 and 5 were used in Examples 4, 5 and 6, respectively. Thedrainage pavement mixtures produced in these Examples 4 to 6 exhibitedexcellent dynamic stability and excellent aggregate-gripping properties.

EXAMPLE 7 AND COMPARATIVE EXAMPLE 6 AND 7

Asphalt compositions were produced in substantially the same manner asin Example 1, except that the formulations as indicated in Table 3 belowwere used. The properties of the asphalt compositions are shown in Table3.

TABLE 3 Comparative Comparative Example 7 Example 6 Example 7 Blockcopolymer Polymer 6 Polymer 6 Polymer 7 Amount of block copolymer 8 8 8(parts by weight) Amount of asphalt 100 100 100 (parts by weight) Amountof sulfur 0.2 0 0 (parts by weight) Softening point (° C.) 102 96 98Melt viscosity (cP) 540 420 430 Penetration ratio (1/10 mm) 42 48 44Elongation (cm) 86 78 79 Adhesion strength (gf/10 mm) 5,300 4,700 3,500Flexural stress (N/mm²) 7.3 6.1 6.4 High temperature Difference in 16 1825 storage softening stability point (° C.)

INDUSTRIAL APPLICABILITY

The asphalt composition of the present invention is advantageous notonly in that it has a high softening point and excellent properties withrespect to ductility, storage stability at high temperatures and that,when the asphalt composition is used in road paving, there can be formeda pavement layer having excellent dynamic stability and excellentaggregate-gripping properties. Therefore, the asphalt composition of thepresent invention is very suitable for use in road paving. Thus, theasphalt composition of the present invention can be advantageously usedas a binder for road paving, especially as a binder for forming adrainage pavement.

1. An asphalt composition comprising: 0.5 to 50 parts by weight of ablock copolymer component (I) comprising at least one terminal-modifiedblock copolymer comprising: a base block copolymer comprising at leastone vinyl aromatic polymer block (A) composed mainly of vinyl aromatichydrocarbon monomer units and at least one conjugated diene polymerblock (B) composed mainly of conjugated diene monomer units, and amodifier group bonded to a terminal of said base block copolymer, saidmodifier group having at least one functional group selected from thegroup consisting of a hydroxyl group, an epoxy group, an amino group, asilanol group and an alkoxysilane group, said base block copolymer beingunhydrogenated or hydrogenated, 100 parts by weight of an asphalt (II),and 0.01 to 10 parts by weight of at least one vulcanizing agent (III)selected from the group consisting of sulfur and a sulfur-containingcompound.
 2. The asphalt composition according to claim 1, wherein saidblock copolymer component (I) is a mixture of: 10 to 90% by weight of aterminal-modified block copolymer (I-A) comprising: a base blockcopolymer comprising at least two vinyl aromatic polymer blocks (A) andat least one conjugated diene polymer block (B), said modifier groupbeing bonded to a terminal of the base block copolymer, and said baseblock copolymer being unhydrogenated or hydrogenated; and 90 to 10% byweight of at least one block copolymer selected from the groupconsisting of: a terminal-modified block copolymer (I-B) other than saidterminal-modified block copolymer (I-A), which comprises: a base blockcopolymer comprising at least one vinyl aromatic polymer block (A) andat least one conjugated diene polymer block (B), said modifier groupbeing bonded to a terminal of the base block copolymer, and said baseblock copolymer being unhydrogenated or hydrogenated, and an unmodifiedblock copolymer (I-C) comprising at least one vinyl aromatic polymerblock (A) and at least one conjugated diene polymer block (B), saidunmodified block copolymer (I-C) being unhydrogenated or hydrogenated,wherein each % by weight is based on the weight of said mixture.
 3. Theasphalt composition according to claim 1 or 2, wherein said modifiergroup has at least one functional group selected from the groupconsisting of the functional groups represented by the followingformulae (1) to (14):

wherein, in the formulae (1) to (14): N represents a nitrogen atom, Sirepresents a silicon atom, O represents an oxygen atom, C represents acarbon atom, and H represents a hydrogen atom, each of R¹ to R⁴independently represents a hydrogen atom or a C₁-C₂₄ hydrocarbon groupwhich optionally has at least one functional group selected from thegroup consisting of a hydroxyl group, an epoxy group, an amino group, asilanol group and a C₁-C₂₄ alkoxysilane group, each R⁵ independentlyrepresents a C₁-C₄₈ hydrocarbon group which optionally has at least onefunctional group selected from the group consisting of a hydroxyl group,an epoxy group, an amino group, a silanol group and a C₁-C₂₄alkoxysilane group, each R⁶ independently represents a hydrogen atom ora C₁-C₈ alkyl group, R⁷ represents a C₁-C₄₈ hydrocarbon group which hasat least one functional group selected from the group consisting of ahydroxyl group, an epoxy group, an amino group, a silanol group and aC₁-C₂₄ alkoxysilane group, and each R⁸ indeDendently represents ahydrogen atom or a C₁-C₂₄ hydrocarbon group.
 4. A method for producingthe asphalt composition of claim 1 or 2, which comprises: (1) providinga living block copolymer comprising: a base block copolymer comprisingat least one vinyl aromatic polymer block (A) composed mainly of vinylaromatic hydrocarbon monomer units and at least one conjugated dienepolymer block (B) composed mainly of conjugated diene monomer units, andlithium ions bonded to the terminals of said base block copolymer, (2)reacting said living block copolymer with a modifier compound having orbeing capable of forming at least one functional group, selected fromthe group consisting of a hydroxyl group, an epoxy group, an aminogroup, a silano group and an alkoxysilane group, to thereby obtain aterminal-modified block copolymer, and (3) adding the obtainedterminal-modified block copolymer and at least one vulcanizing agent toa molten form of an asphalt while stirring, said at least onevulcanizing agent being selected from the group consisting of sulfur anda sulfur-containing compound.
 5. The method according to claim 4,wherein said terminal-modified block copolymer obtained in step (2) issubjected to hydrogenation.
 6. The asphalt composition according toclaim 1, wherein said modifier group is bonded to said at least onevinyl aromatic polymer block (A) of said base block copolymer.